Agricultural inorganic fertilizers typically include a base comprising at least one of three primary inorganic nutrients—nitrogen (N), phosphate (P), and potassium (K). These fertilizers are identified by their NPK rating in which the N value is the percentage of elemental nitrogen by weight in the fertilizer, and the P and K values represent the amount of oxide in the form of P2O5 and K2O that would be present in the fertilizer if all the elemental phosphorus and potassium were oxidized into these forms. The N—P—K proportions or concentration vary across fertilizer types and user needs.
For example, the base fertilizer can comprise a phosphate fertilizer (such as monoammonium phosphate (“MAP”), diammonium phosphate (“DAP”)), a potash fertilizer (such as muriate of potash (“MOP”)) or other potassium-based fertilizer, or a nitrogen-based fertilizer such as a fertilizer containing urea. The fertilizers can also include any combination of secondary nutrients and/or micronutrients. The secondary nutrients can include sulfur compounds, calcium, and/or magnesium, and the micronutrients can include iron, manganese, zinc, copper, boron, molybdenum, and/or chlorine. The micronutrients and/or secondary nutrients can be added to solution in their elemental form, or as compounds, such as a salt.
Many of these agricultural fertilizers are granulated, dried, and treated with dust control agents after formulation to provide the fertilizer in a stable and easily handled form. An inherent drawback of the conventional granulation process is that a significant portion of the fertilizer may generate dust particulates either during manufacture, storage, or in distribution, which is significantly more difficult to handle and distribute on the fields to be treated. In addition to wasting otherwise useful fertilizer, the fertilizer may create undesirable fugitive particle emissions. Fugitive particulate emissions can be mitigated, but in certain conditions mitigation costs can become uneconomical.
To reduce the dust generation, the fertilizer granules are often coated with an anti-dust coating that reduces or entraps the dust created during the granulation or transport. The anti-dust coating can comprise, for example, petroleum, wax, or other oil-based liquids that are sprayed onto the fertilizer granules to adhere any dust particulates formed, during granulation or transport, for example, to the larger fertilizer granules. The coating also encapsulates the dust particulates to prevent or inhibit the dust particulates from becoming airborne.
While traditional coatings are effective at controlling the dust particulates, the inherent drawback of these coatings is that the coatings have a limited effective shelf-life and can have diminishing effectiveness as the coating ages. Prolonged storage or transport of the coated fertilizer can present a greater safety risk as the storage or transport time may have exceeded the effective life of the coating resulting in unsafe fertilizer products, and/or undesirable flow characteristics in storage bins, transportation equipment, and field application equipment. Furthermore, these traditional coatings can potentially add significant cost to the end-product due to the cost of the coating composition and/or increased manufacturing costs. Alternative dedusting agents with extended shelf life are commercially available but these products tend to have substantially higher cost and for this reason have not been broadly adopted by the industry.
As such, there is a need for a means of efficiently and effectively reducing dust generated during the handling of granular fertilizers and/or to increase the agricultural benefits of the fertilizer.